current_users = ['admin', 'ZHANGSAN', 'lisi', 'wangwu', 'zhaoliu']
current_users_backup = [user.lower() for user in current_users]
print(current_users_backup)
new_users = ['admin', 'Zhangsan', '青龙', '白虎', '朱雀']
for user in new_users:
	if user.lower() in current_users_backup:
		print(f"{user} 已被使用，需要输入别的用户名")
	else:
		print(f"{user}未被使用")
